1. Field of the Invention
The present invention relates to a reversal color development process. More particularly, the invention relates to a reversal color photographic process for providing color photographic images having an improved multilayer effect, granularity, and sharpness.
2. Description of the Prior Art
A reversal color development process for multilayer silver salt color photographic materials is described in, for example, C. E. K. Mees, The Theory of the Photographic Process, 2nd, Ed., Paragraph 25, 1954. As such a development process, there are generally two systems: a reversal development process wherein the color development is carried out with couplers in the photographic emulsion layers of color photographic materials; and a reversal development process wherein the color development is carried out with couplers in the developer. In both systems, processing is composed of the following steps.
An exposed color photographic material is subjected to a first development using a black and white developer, whereby silver salt in exposed areas is reduced to form a negative image. Then, the photographic material is subjected to color development, whereby unexposed silver halide which was not reduced in the first development is developed to form developed silver and, at the same time, oxidized color developing agent is caused to react with couplers to form a positive color image. Thereafter, silver is removed in a silver removal step to leave a sharp dye image on the support of the color photographic material. The silver removal step may be a bleach step to convert developed silver to a water-soluble or water-insoluble silver salt by oxidizing it and a fix step to dissolve the water-soluble silver salt or to convert the water-insoluble silver salt to a water-soluble silver complex salt followed by dissolution of the water-soluble silver complex salt or, alternatively, may be a blix step which accomplishes the bleach step and the fix step in one step.
In any case, the first development (or black and white development), color development, and silver removal are the fundamental steps of a reversal color development but the process may further include, if desired, auxiliary steps such as a stopping, a hardening, a stabilization, etc.
The reversal development of the type where the color development is carried out with couplers in the developer includes a cyan development, a yellow development, and a magenta development, and each color developer contains the corresponding coupler therein. On the other hand, in the reversal development of the other type, the color photographic material contains the couplers in its photographic emulsion layers.
One of the important concepts of the latter type of reversal color development is to effectively perform the second development (color development), and for this purpose a chemical fogging is usually employed after the first development of the color photographic material instead of a light fogging. In order to perform chemical fogging, ethylene diamine, n-butylamine, an alkali metal salt of borohydride, amine borane, etc., are added alone or as a mixture thereof to the second developer or color developer as a fogging agent.
On the other hand, a technique has recently been utilized where a development inhibitor is released from the developed layer containing it as the development progresses, and the development of an adjacent photographic emulsion layer is inhibited to give the multilayer effect or the development of the layer containing the development inhibitor or the layer adjacent thereto is inhibited to give fine granularity. A compound which releases a development inhibitor in the development reaction is called "development inhibitor releasing compound" or a "DIR compound;" such a compound may be a coupler, a developing agent, or a material which releases an inhibiting compound upon development.
Since such DIR compounds are used in color photographic negative materials, it might be considered obvious to utilize DIR compounds in reversal color development to obtain an improved multilayer effect and fine granularity, but the practical application of this technique encounters problems. That is, the effect of the DIR couplers used in the first development also affects the subsequent steps to inhibit a sufficient color development. This phenomenon is also observed in a color developer containing a fogging agent, as mentioned above. Therefore, it has been difficult with conventional techniques to use DIR materials with color negative materials in reversal color photographic systems for industrial or commercial purposes. Even if the DIR couplers are used in reversal color photographic materials, they can be used only in the range which does not inhibit the color development, and hence their effect is low.
If the remarkable effect of DIR compounds in negative color development could be achieved in reversal color processing, the quality of the color images would be markedly improved.
The application of DIR couplers to development processes for reversal color photographic materials also encounters problems in granularity and color image sharpness, i.e., when the color development is inhibited, it is observed that the granularity of color images formed is roughened to reduce the sharpness thereof. The reason for this effect is not completely clear, but it is believed that if a development inhibitor is strongly adsorbed around silver salt grains, the number of development initiation points is lessened and the dyes formed concentrate around the development initiation points, which results in an enlarging of dense dye distribution points to coarsen the granularity and reduce the sharpness of the color images. From this viewpoint, the use of DIR compounds in reversal color photographic development actually decreases image quality.